linux-kernel - Re: [PATCH v3] err.h: allow IS_ERR_VALUE to handle properly more types

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Message-id: <56BDF012.2000503@samsung.com>
Date:	Fri, 12 Feb 2016 15:45:38 +0100
From:	Andrzej Hajda <a.hajda@...sung.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	open list <linux-kernel@...r.kernel.org>,
	Bob Peterson <rpeterso@...hat.com>, linux@...musvillemoes.dk
Subject: Re: [PATCH v3] err.h: allow IS_ERR_VALUE to handle properly more types

On 02/11/2016 05:39 PM, Arnd Bergmann wrote:
> On Thursday 11 February 2016 08:00:54 Andrzej Hajda wrote:
>>> I think the easiest way to express this would be to ensure that the argument
>>> is 'unsigned long', like:
>>>
>>> #define IS_ERR_VALUE(x) ((unsigned long*)NULL == (typeof (x)*)NULL && \
>>>        unlikely((unsigned long long)(x) >= (unsigned long long)(typeof(x))-MAX_ERRNO))
>> This way you will limit it only to unsigned long type, which seems too
>> strict to me.
>> I think the macro should accept all long enough unsigned types, otherwise we
>> could end up with bunch of macros IS_ERR_VALUE_U32, IS_ERR_VALUE_ULL...
> I think in practice we only care about 'int' and 'unsigned long', which are
> the ones that 90% of the existing users pass in today. u32 has never worked
> on 64-bit architectures so far, so we don't necessarily have to make it work.
> As Al mentioned, most users of IS_ERR_VALUE are wrong anyway and should
> just use 'if (err < 0)' or 'if (err)'.
>
> We could also consider making just 'int' and 'unsigned long' allowed types
> for the moment, and then change all users passing 'int' before forbidding them.
>
> 	Arnd
>
>

OK so in short we need to fix 140 usages of the macro? Who should do them?
I can create cocci patch for more obvious cases. What about these less
obvious?
As I understand we do not touch the macro till fixes are merged?

Regards
Andrzej